When can I put my child in a booster seat in Washington State?

In the State of Washington, children can move to a booster seat when they reach the top height or weight limit allowed by your forward facing car seat’s manufacturer. Additionally, all children under the age of 13 must be securely fastened in the car’s back seat.

No person may operate a motor vehicle unless all children passengers under the age 16 are either wearing a safety belt or are securely fastened in an approved child restraint device. – Washington’s Seat Belt Law(RCW 46.61.688